The central hypothesis of this project is that vascular wall endothelial and smooth muscle cells (SMC) are part of a complex and highly regulated innate immune system that modulates inflammatory signaling in atherosclerosis. We have discovered that human coronary artery SMC (HCASMC) express membranebound CD14, a pattern recognition receptor that plays a central role in transducing innate immune responses to endotoxin and other bacterial products in inflammatory cells. We have also detected expression in vascular cells of surfactant protein D (SP-D), a member of the collectin family of proteins that binds to endotoxin and CD14 to modulate innate immune responses in the lung. Using a combination of pharmacological, molecular, and gene-based approaches, we propose to: 1. Test the hypothesis that CD14 in SMC plays a central role in transducing immune responses to multiple inflammatory mediators. We will identify CD14 ligands in HCASMC, and we will examine regulation of CD14 expression in HCASMC and human coronary artery endothelial cells by oxidative stress and activation of PPAR-gamma. We will also determine whether CD14 ligation modulates expression and function of scavenger receptors in SMC. 2L Test the hypothesis that SP-D modulates CD14-mediated pro-inflammatory signaling in vascular cells. We propose to examine mechanisms whereby SP-D blocks pro-inflammatory signaling in vascular cells, focusing on the role of binding of SP-D to endotoxin and cell signaling proteins. We will also determine whether SP-D expression is regulated by inflammatory mediators and/or oxidative stress. 3. Test the hypothesis that CD14 and SP-D modulate atherosclerosis in apoE-/- mice. Using CD14-/- and SP-DV-/- mice cross-bred with apoE-/- mice to create double knockout mice, we will examine the extent of atherosclerosis, vascular inflammation, and endothelial dysfunction in the absence and presence of recurrent challenges with low-level endotoxin to stimulate the innate immune system. Together, the proposed studies will provide novel insight into the potentially critical role of CD14 in vascular inflammation, and modulation of CD14 expression in the vascular wall by oxidant stress and PPAR-gamma. Further, the proposed studies will be the first to investigate the potential immunomodulatory role of SP-D in the vascular wall. These studies will help to elucidate mechanisms whereby vascular wall cells contribute to inflammation now known to be an important cause of atherosclerosis. Further, our findings may lead to new approaches to treating the inflammatory component of atherosclerosis.